A battery pack mounted on a vehicle supplies electric energy to various loads such as an engine starter, and electric energy is supplied (charged) to the battery pack from a vehicle generator (alternator). There has been known a battery pack which mounts a battery management device and a current cutoff device therein. The battery management device manages a secondary battery formed of energy storage devices, and the current cutoff device cuts off an electric current supplied to the secondary battery. When the battery management device detects abnormality in the secondary battery, the supply of an electric current to the secondary battery is cut off by the current cutoff device. See JP 2013-195183 A.